1. Field of the Invention
This invention relates to a fuel injection system for an internal combustion engine and improvement of the fuel economy thereof
2. Prior Art Statement
It is known that cooling of the fuel injector assures proper functioning of the injector and that by moving a sufficient amount of fluid through a passage adjacent the injector provides a cooling effect, however, Stockner, et al., in their the U.S. Pat. No. 4,267,977 admit that auxiliary cooling such as a heat exchanger may be needed in the return line to supplement cooling.
It has long been recognized that fuel injected engines consume a lower amount of fuel and operate more smoothly when the fuel temperature to the injectors is controlled and more specifically when the temperature of the fuel at the injector is kept below 50xc2x0 C. (120xc2x0 F.). For instance, DeKeyser, et al., U.S. Pat. No. 4,222,713 issued on Sep. 16, 1980, recognized that power loss occurs at a fuel temperature above 50xc2x0 C. (120xc2x0 F.) as the fuel mass changes inversely with temperature. DeKeyser, et al., thus increase the amount of fuel injected with increased temperature by varying the injector pumping stroke length using a bellows responsive to fuel temperature.
Robert S. Keane, in his U.S. Pat. No. 4,385,615 issued on May 31, 1983 states that horsepower output of Cummins engines decreases by 1% with each 10xc2x0 F. (5.5xc2x0 C.) rise in temperature above 94xc2x0 F. (34.4xc2x0 C.). Keane further states that Cummins engines operate best with a fuel temperature in the range from about 94xc2x0 F.-104xc2x0 F. (34.4-40xc2x0 C.) and therefore provides an auxiliary fuel tank of limited volume for receiving return flow from the injectors of the engine wherein the auxiliary fuel tank may be heated or cooled to maintain the fuel fed to the injectors in the desired temperature range.
Auxiliary temperature control systems for fuel being returned to the tank are also known. For instance, in the U.S. Pat. No. 4,872,438 issued on Oct. 10, 1989, Ausiello, et al., senses the temperature of the fuel in the supply circuit downstream of the pump and provides for cooling of fuel being returned to the tank in response to signals provide by the temperature sensor. Ausiello, et al., also provide means for returning a portion of the pump output to the inlet of the pump through a branch line to increase fuel temperature.
Kawai, et al., U.S. Pat. No. 4,522,177, issued on Jun. 11, 1985, also recognized that the quantity of fuel injected decreases with a rise in fuel temperature and therefore compensate for the decreased fuel supply by providing means for increasing the quantity of fuel supplied by the fuel supply means when the temperature of the fuel in the fuel supply line to the injectors is greater than 40xc2x0 C. (104xc2x0 F.) but does not address increasing the flow of fuel returned to the fuel tank when the supply volume is already sufficient.
Charles Tuckey, in his U.S. Pat. No. 4,926,829 issued on May 22, 1990, detects the flow of fuel through the return line and adjusts the pump output volume as an inverse function of the return fuel flow. Thus, although Tuckey reduces the amount of heated fuel returned to the tank, the temperature of the returned fuel is most likely higher.
To provide for a substantially even horsepower output from each cylinder in a Caterpillar 3406E diesel engine, Cleveland, et al., in the U.S. Pat. No. 5,865,158 issued on Feb. 2, 1999 adjust the pulse width at each injector based on a calculated temperature at each injector. The calculated temperature is a linear extrapolation of the difference between the outlet temperature and the inlet temperature of the fuel rail.
Those skilled in the art also know that voids or gas bubbles in high pressure fuel systems hamper the injection of fuel to the combustion chambers. Bally, et al., in U.S. Pat. No. 4,577,237 issued on Dec. 10, 1985 control cavitation within the high pressure injection pump by providing a spill passage for communicating a bypass port with a low pressure chamber of the pump to flush out entrained air prior to the next pump stroke. Keane, in the aforementioned U.S. Pat. No. 4,385,615, maintains the level of fluid in the auxiliary tank at the same level as the pump to reduce entrained air.
Finally, the inventors of the instant invention have previously increased horsepower output of truck engines using a fuel rail system where each injector is fed by an individual injector pump by increasing the diameter of an orifice in the fuel system return line and increasing the fuel volume flowing through the fuel rail thereby increasing the volume flow of fuel returned to the fuel tank that also resulted in a decreased temperature of the returned fuel.
The aforementioned prior art described certain methodologies of cooling returned fuel for the purposes of cooling injectors or increasing horsepower in fuel injected engines, however, the synergy between increased fuel return flow at an adequate supply volume, decreased fuel temperature, decreased fuel aeration and increased horsepower while maintaining sufficient pressure at the fuel rail has not been recognized.
Therefore, it is an object of this invention to decrease the temperature of the fuel returned to the tank from an injection system fuel rail while maintaining a given pressure at the fuel rail.
It is also an object of this invention to decrease the temperature of the fuel returned to the tank from an injection system fuel rail by increasing the flow rate of fuel being returned to the tank.
Yet a further object of this invention is to increase the flow through the fuel rail back pressure valve by increasing the inlet diameter of the back pressure valve.
Still a further object of this invention is to increase the flow through the fuel rail back pressure valve by increasing the diameter of the outlet holes in the back pressure valve.
A principal object of this invention is to increase the fuel economy of a diesel engine having an injection fuel rail by increasing the amount of fuel returned to the fuel tank from the fuel rail.
A significant object of this invention is to increase the fuel economy of a Caterpillar 3406E series diesel engine up to 10 percent.
Another significant object of this invention is to increase the fuel economy of a diesel engine having an injection fuel rail by decreasing the fuel temperature in the tank and hence the fuel temperature at the inlet of the fuel rail.
Still another significant object of this invention is to increase the fuel economy of a diesel engine having an injection fuel rail by returning sufficient fuel to the tank to maintain a temperature in the fuel tank at substantially ambient temperature.
Yet another principal object of this invention is to increase the fuel economy of a diesel engine having an injection fuel rail by decreasing the amount of fuel aeration at each injector successive to the first injector by increasing the mass flow through the fuel rail.
It will be recognized that another object of this invention is to increase horsepower and fuel economy in a diesel engine having an injection fuel rail using the synergistic effect of increasing fuel return flow to the tank, decreasing fuel temperature of the returned fuel while maintaining sufficient pressure in the fuel rail.
Additionally, it will be recognized that another object of this invention is to increase horsepower and fuel economy in a diesel engine having an injection fuel rail using the synergistic effect of increasing fuel return flow to the tank, decreasing fuel aeration at successive injectors after the first injector, substantially maintaining a constant fuel temperature to the inlet of the injection rail while maintaining sufficient pressure in the fuel rail.
Other objects of this invention will become readily apparent upon a reading of the following specification and reference to the drawings made a part hereof